How NASA recovered from tragedy and tackled the job of getting the shuttle flying again.

There's no doubt that the next shuttle flight will be the most carefully watched in history. To the 14 tracking cameras active at the Florida launch site, NASA is adding nine more. There are new cameras on the external tank and solid rocket boosters, and more are planned. Department of Defense telescopes, which could have seen the damage done to Columbia's wing had NASA requested photographs of the craft while it was in orbit, will view every shuttle from now on as a matter of course. (The CAIB censured the STS-107 mission controllers for not availing themselves of these assets after seeing foam fall from the tank.)

If a strike should occur during launch, its impact will be detected by 88 accelerometers and temperature sensors newly installed inside the wing. Even if the sensors register no impact, the astronauts, once in orbit, will deploy a new piece of hardware, the Orbiter Boom Sensor System. Attached to the shuttle's robot arm, the 50-foot boom carries two laser imaging systems and a low-light black-and-white television camera that will scan the shuttle's nose cone and the 44 RCC panels on the wings' leading edges to provide three-dimensional maps of those areas.

In addition, on flight day three, before Discovery docks with the space station, STS-114 Commander Eileen Collins will perform a pitch-around maneuver 600 feet from the station, exposing the craft's tiled underside to photography by the station crew. The two astronauts on the station will have about 100 seconds, as the shuttle turns a slow somersault at a rate of .75 degree per second, to scan the shuttle's underside for damaged tiles and take pictures of specific areas, like the seals over the main landing gear, that experience high heating. "They will almost immediately downlink those digital photos to mission control," says Collins, "and once we've docked, we'll be able to go into the space station and see the pictures."

Collins is pure astronaut. A thoughtful, exuberant pilot, with the no-problem-too-big attitude the astronauts are famous for, she is the only woman to have commanded a space shuttle mission. STS-114 will be her second command. (She is also a mother of two, and there is a remarkable interview on NASA's Web site in which she describes explaining the Columbia accident to her eight-year-old daughter.) The pitch-around maneuver has never been done, and Collins admits, "Initially it was a big concern to shuttle management." In fact, it violated one of the program's long-standing safety rules: When a shuttle is in close proximity to another spacecraft, the target must be in sight at all times. For this maneuver, the space station will be out of the astronauts' view for six or seven minutes.

Over time, shuttle managers have satisfied themselves that the risk is acceptable. "I've been flying this [in the simulator] for over a year and a half," Collins says. "We've made some good changes to make it safer." Even if the astronauts spot trouble during the inflight inspections, they won't be able to repair the kind of damage that brought down Columbia. With just months left before the STS-114 launch, NASA and its contractors were still struggling to develop materials and techniques to repair tiles and RCC.

"The space agency gave up on tile repair in the 1980s as an impossible task," says NASA's Wayne Hale. Although some progress has been made since, in an emergency the STS-114 astronauts will have only a minimal repair capability-applying a patch or using a kind of caulk gun to fill holes were the two leading repair methods proposed as of early this year. This CAIB mandate has proven among the hardest to meet, and NASA may only be able to satisfy the letter-of-the-law requirement for a "capability to effect emergency repairs." Foreseeing the difficulties with repair, NASA added another safety measure for STS-114: the rescue shuttle. If the astronauts make it to orbit but can't return to Earth, they will dock with the International Space Station and wait for another shuttle to arrive and take them home. The station has enough oxygen, food, and other supplies to host seven refugees for 45 days.

Early last year, in a self-imposed directive, shuttle program managers decided to make rescue capability a requirement for the first few flights. Dick Covey's Return to Flight Task Group has endorsed the idea. Yet when Covey piloted Discovery after the Challenger accident, there was no space station to offer shelter and no second shuttle ready to rescue him and his crew. His commander on that flight was Rick Hauck, a veteran of three shuttle flights and now the president and CEO of AXA Space in Bethesda, Maryland, which insures commercial satellites. Hauck, who has led National Research Council studies on space program risks, calls himself an interested but distant observer of the return-to-flight process. I asked him why he thought a safe haven was required now, when it hadn't been for his flights.

"After Challenger we were dealing with an accident that destroyed the shuttle going uphill," he says. "So the question of being safely in orbit and then being able to be rescued was not deemed to be the highest likelihood. Columbia changed that thinking."

What has not changed, despite Columbia, is the judgment that the ascent to orbit is the most dangerous phase of any shuttle flight. According to NASA's risk assessments, the solid rocket motors and space shuttle main engines are as likely to cause a catastrophic accident as all other shuttle systems combined.

Launching a second shuttle is an action that would be taken only in the direst emergency and, as NASA has admitted in its implementation plan, would put the second crew at risk. "I'm sure the astronauts would take that risk in a moment," says Henry McDonald, former director of NASA's Ames Research Center in California and now a professor of engineering at the University of Tennessee. "The question is whether we ought to let them."